[Federal Register Volume 59, Number 220 (Wednesday, November 16, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-28243]
[[Page Unknown]]
[Federal Register: November 16, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 90-NM-265-AD; Amendment 39-9073; AD 94-23-10]
Airworthiness Directives; Boeing Model 727 Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment supersedes an existing AD that currently
requires periodic leak checks of the forward lavatory drain system and
provides for the installation of a new drain valve as terminating
action. This action continues to require various leak checks, but
deletes a previously provided terminating action; adds requirements for
leak checks of other lavatory drain systems; provides for the option of
revising the FAA-approved maintenance program to include a schedule of
leak checks; requires the installation of a cap on the flush/fill line;
and requires either a periodic leak check of the flush/fill line cap or
replacement of the seals on both that cap and the toilet tank anti-
siphon (check) valve. This amendment was prompted by continuing reports
of damage to engines and airframes, separation of engines from
airplanes, and damage to property on the ground, caused by ``blue ice''
that had formed from leaking forward lavatory drain systems and
subsequently had dislodged from the airplane. The actions specified by
this AD are intended to prevent such damage associated with the
problems of ``blue ice.''
EFFECTIVE DATE: December 16, 1994.
ADDRESSES: The service information referenced in this AD may be
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle,
Washington 98124-2207. This information may be examined at the Federal
Aviation Administration, (FAA), Transport Airplane Directorate, ANM-
103, Attention: Rules Docket No. 90-NM-265-AD, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056. Comments may be inspected at this
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT: Don Eiford, Aerospace Engineer,
Seattle Aircraft Certification Office, Systems and Equipment Branch,
ANM-130S, FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW.,
Renton, Washington 98055-4056; telephone (206) 227-2788; fax (206) 227-
1811.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations to add an airworthiness directive (AD), applicable
to Boeing Model 727 series airplanes, was published as a supplemental
notice of proposed rulemaking (NPRM) in the Federal Register on March
18, 1994 (59 FR 12865). That supplemental NPRM proposed to supersede AD
86-05-07, amendment 39-5250 (51 FR 7767, March 6, 1986). That AD
currently requires periodic leak checks of the forward lavatory drain
system and provides for the installation of a new drain valve as
terminating action.
Among other things, the supplemental NPRM proposed to:
1. Delete the existing provision for terminating action;
2. Require repetitive leak checks of both the forward and the aft
lavatory drain systems;
3. Provide an optional procedure for complying with the rule, which
would entail revising the FAA-approved maintenance program to
incorporate a schedule and procedure to conduct leak checks of the
lavatory drain systems; and
4. Require the installation of a lever lock cap on flush/fill
lines, and periodic leak check of the flush/fill line.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
Personal Injury Risk of Blue Ice
Several commenters request that all actions applicable to the aft
lavatory drainage systems be deleted from the proposed rule, since the
risk of injury caused by ``blue ice'' forming at an aft lavatory,
dislodging from an airplane, and striking a person on the ground is
extremely remote. As justification for their request, these commenters
cite an analysis that was performed in 1990 to determine the
probability of personal injury. This analysis concludes that such
probability is on the order of 1 x 10-9 per flight.
The FAA does not concur with these commenters' request. The
criteria of a probability of injury being on the order of 1 x
10-9 per flight hour is relevant when an aircraft system is
originally certified. However, once an unsafe condition becomes known
to the FAA, an analysis is not necessarily sufficient to refute the
unsafe condition. The FAA considers that the numerous reported cases of
``blue ice'' striking and damaging houses, cars, and populated areas is
sufficient to support the conclusion that ``blue ice'' falling from aft
lavatory drain systems presents an unsafe condition.
Moreover, the FAA does not find the analysis submitted by the
commenters to be conclusive. That particular analysis was based on
several assumptions whose adequacy the FAA questions. Among them are:
1. The analysis assumed that a piece of ``blue ice'' falls to the
ground once every two weeks in the United States. These figures were
based upon language that appeared in a newspaper article and are
apparently anecdotal data. The FAA points out that the cases addressed
in the newspaper article (and, therefore, in the analysis) may be only
the ``reported'' cases; however, the vast majority of cases go
unreported, and are likely to be on the order of many magnitudes
greater than the number reported.
2. Additionally, the crux of the analysis is based on assumptions
that the size of a shadow of a person on the ground is two square feet.
This appears to assume that the person is standing up, the ice comes
straight down, the ice falls as a single projectile, and the ice does
not break into smaller pieces as it comes through a roof and ceiling.
None of these assumptions are proven or representative of a typical
scenario.
Further, the FAA points out that demographic studies have shown
that population density has increased around airports, and probably
will continue to increase. These are populations that are at greatest
risk of damage and injury due to ``blue ice'' dislodging from an
airplane during descent. Without actions to ensure that leaks from the
aft lavatory drain systems are detected and corrected in a timely
manner, ``blue ice'' incidents would go unchecked and eventually
someone would be struck, perhaps fatally, by falling ``blue ice.'' To
discount the unsafe condition to persons on the ground presented by
falling ``blue ice'' would be a gross breach of the FAA's safety
obligations and commitment to the public.
Reliability Targets for Leak Check Intervals
One commenter requests that the FAA provide reliability targets so
that operators would know what data were necessary to obtain FAA
approval of any request for an extension of a leak check interval. The
FAA cannot concur with the commenter's request. The FAA has not
provided such a ``reliability target'' because of the difficulty
involved in specifying a target that would be applicable to and
appropriate for all or most operators. While the FAA recognizes that
larger operators are more likely to be able to provide a statistically
significant data package, it considers that the approach to the
development of ``reliability targets'' must also allow smaller
operators to participate. For these reasons, and until a universal
reliability target program can be developed, the FAA will review
individual requests on a case-by-case basis. Paragraph (c) of the final
rule provides for the submission of data to be considered for the
approval of extensions to leak check intervals; these data can be
summarized and accompanied by recommendations from industry groups.
Data From Boeing Model 737's
One commenter requests that the FAA consider data from Boeing Model
737 airplanes, in conjunction with data from Boeing Model 727
airplanes, when reviewing requests to extend the leak check interval.
The FAA points out that, even though the design of the Model 727 and
Model 737 are not similar in many aspects, the functioning of the
lavatory drain systems on both models may be similar due to the
similarity of the hardware used. Therefore, the FAA will consider data
from similar drain systems of different airplane models when reviewing
requests received to extend leak check intervals; however, in
accordance with the data gathering requirements of paragraph (c) of
this final rule, any data submitted must reflect which airplanes and
which drain valves the data represent.
Boeing Specifications vs. Brand Name Valves
Several commenters request that the proposed rule be revised so
that affected hardware is identified by Boeing Specification number,
rather than by vendor part numbers. These commenters are concerned that
certain parts may not qualify for longer inspection intervals because
they have dash numbers not called out specifically in the proposed
rule. They consider that this is not only confusing, but inequitable,
since many later hardware configurations will fall into the ``any other
type valve'' category that provides for a leak check interval of only
400 flight hours. The commenters consider that requesting ``alternative
methods of compliance'' will become the norm, unless the rule is
revised to refer to hardware specification numbers. One commenter, a
manufacturer of valves, is concerned that it will be unable to market
its equipment because the proposed rule provides no performance
standards under which its valves can qualify.
On the other hand one commenter objects to the FAA's statement in
the preamble to the supplemental NPRM that indicated, ``* * * One of
the factors that the FAA will consider in approving alternative valve
designs is whether the valve meets Boeing Specification S417T105 or 10-
62213.'' This commenter interprets the phrase to be a requirement for
Boeing approval of any alternative valve only to the Boeing
specifications.
The FAA does not concur with the commenters' requests to call out
valves by Boeing specification only. Boeing specifications were not
referenced in this final rule because the FAA does not consider it
appropriate for Boeing to screen and potentially disapprove, for
purposes of this AD, alternative valves that may not qualify to
Boeing's specifications. This would have the effect of delegating to
Boeing, through its specification qualification procedure, the
authority to approve or disapprove alternative methods of compliance
with this AD. Approval under a Boeing specification is not a
requirement for a valve design under this rule; it is only a factor to
be considered. Other factors may be taken into account as well, such as
having extensive service history data. Review and approval of
alternative valve designs is a function of the FAA through the
``alternative methods of compliance'' procedures provided by paragraph
(f) of the final rule. The wording of the NOTE 7 following paragraph
(f) of the final rule has been revised to clarify this point.
Qualifying For 1,000 Flight Hour Leak Check Interval
Several operators request that the proposed rule be revised to
include a provision that would allow any service panel drain valve,
manufactured by any manufacturer, to become qualified for the 1,000-
flight hour leak check interval. These commenters state that, by
restricting the 1,000-flight hour interval to only certain brand name
valves, the FAA restricts competition that could lead eventually to the
development of better valves.
The FAA does not agree that the 1,000 flight hour leak check
interval should be allowed unequivocally for all service panel drain
valves. Current service history data indicate that some valves are more
reliable than others; those valves that have demonstrated such
reliability in service so far are the valves identified (by brand name)
in this rule. The FAA does not consider that a design review and
qualification test are sufficient to determine how well a valve will
perform in actual service. This has been clearly demonstrated by the
history of this specific AD action: the installation of any of several
valves was designated previously as terminating action for the required
leak check, but those valves were later found to be subject to leakage.
However, the FAA does agree that requirements for service history data
should not be so rigid as to preclude competition by valve
manufacturers with new designs. Therefore, the FAA will consider
requests for inclusion in the 1,000-flight hour leak check category any
valve for which the design, qualification test, and service history
data are provided. The request should include an analysis of known
failure modes for the valve and failure modes of similar valves; an
explanation should be included as to how the design features of the
valve will preclude these failure modes. Also included should be the
results of qualification tests, and service history data covering
approximately 25,000 flight hours or 25,000 flight cycles (including a
winter season), collected in accordance with the requirements of
paragraph (c) of the final rule, or a similar program. The final rule
has been revised to include a new NOTE 7 to specify the request for
this information. -
Further, the FAA notes that one operator and a manufacturer,
Pneudraulics, already have provided these data to the FAA, and the
final rule has been revised to add certain Pneudraulics valves to the
category of valves subject to a 1,000-flight hour leak check interval.
(Without the submission and approval of this data, these valves would
have been required to be leak checked at the 200-flight hour interval.)
Differences Between Paragraphs (a) and (b) of the Rule
One commenter maintains that the FAA's safety objective in
addressing the ``blue ice'' issue should be to ensure that each and
every operator has a comprehensive lavatory drain service program in
place. The commenter points out that the FAA attempted this approach
under the provisions of proposed paragraph (b), but made the conditions
of compliance more stringent than those of proposed paragraph (a), such
that no operator would elect to comply with paragraph (b). The
commenter considers this unfortunate since it will result in a less
effective ``blue ice'' prevention program fleetwide.
The FAA acknowledges that a difference exists between the
provisions of paragraphs (a) and (b), both in the supplemental NPRM and
in this final rule. However, as explained elsewhere in this preamble,
the FAA has revised several requirements of paragraph (b) of the final
rule to make it more ``attractive'' to operators. Certain of these
revised requirements include extended leak check intervals for some
valves. The FAA does consider that revising the maintenance program to
include the procedures specified in paragraph (b) will be more
effective overall in addressing ``blue ice'' as an on-going issue. The
provisions of paragraph (b) are more comprehensive in approach: they
include requirements not only for leak checks of the valves, but
replacement of valve seals, repetitive visual inspections for leakage,
procedures for reporting leakage, and training programs to inform
pertinent personnel on ``blue ice'' awareness.
The FAA considers that it is appropriate to maintain the provisions
of paragraph (a) as an option, so that operators without an FAA-
approved maintenance program will have some means to comply with the
rule.
Along this same line, another commenter points out other
differences between the provisions of paragraphs (a) and (b). The
commenter indicates that any valve service history data that is
gathered by an operator complying with paragraph (a) may not be as
valuable as data gathered by an operator complying with paragraph (b).
Unless there is a specific, scheduled maintenance program, there is no
way to determine if a valve may have begun leaking before a leak check
was conducted and was subsequently repaired; therefore, merely passing
a leak check successfully, as under the provisions of paragraph (a),
does not verify the valve's reliability. The FAA acknowledges this
commenter's observations. However, the FAA expects that some operators
will choose to comply with the provisions of paragraph (b) and will
provide the FAA with valve service history data. These data may
indicate that the current leak check intervals are acceptable for
operators operating under a maintenance program, but should be
shortened for operators without a maintenance program. If, as the
commenter suggests, leak tests alone prove to be inadequate to prevent
``blue ice'' formation, the FAA may consider revising this rule at a
later time to modify or delete paragraph (a).
Alternative Recordkeeping
Several commenters request that a revision be made to proposed
paragraph (b) that would allow for the use of an alternative method of
recordkeeping to that otherwise required by Federal Aviation
Regulations Sec. 121.380 (14 CFR 121.380), ``Maintenance recording
requirements''. The commenters' main concern is that it should be clear
to the cognizant Principal Maintenance Inspectors (PMI), and other FAA
officials in the years ahead, that once the maintenance program
revision is made and approved, the AD is ``signed off as complete.'' No
other special records should be required to track the various tasks
specified in proposed paragraph (b) (such as valve seal replacement,
training, reporting procedures, visual checks, etc.), which are in
addition to the recordkeeping requirements that now exist within each
of the affected operator's maintenance program.
The FAA does not concur with the commenters' request for many of
the same reasons it did not concur with a similar request made in
response to the previous supplemental NPRM. The FAA considers that,
even though this AD would affect the maintenance program, it is of such
importance that it warrants other than ``normal'' procedures to be
followed in certain aspects. Some method of recordkeeping must be
maintained to ensure that the required valve seal changes and periodic
leak checks continue, and to ensure that the procedures required by
this AD are not eventually dropped from any operator's maintenance
program.
Principal Maintenance Inspector Involvement
These same commenters request that a statement be added to proposed
paragraph (b) to indicate that the ``AD is no longer applicable once a
revision to the FAA-approved maintenance program is implemented.''
These commenters indicate that it would be less cumbersome to operators
to accomplish all of the AD-required tasks within the parameters of
their FAA-approved maintenance program, where the cognizant PMI would
be the FAA official permitted to approve any further changes to the
program. These commenters contend that it is much more appropriate for
the PMI, rather than the Seattle Aircraft Certification Office (ACO)
engineering staff, to approve subsequent changes to the program once
the program has been approved. The commenters consider that the PMI is
more qualified than the ACO staff to approve tasks on training,
reporting, and adjustments to the leak check intervals based upon
reliability program recommendations. The commenters point out that the
subject matter of the rule is clearly maintenance-related, and the ACO
staff is not equipped to effectively respond to requests for
maintenance interval changes that may occur.
The FAA does not concur with this request for the same reasons it
did not concur with a similar request made by these commenters to the
previous supplemental NPRM. While the FAA agrees that the PMI may be
permitted certain oversight of the proposed alternative maintenance
program provision of the rule (specifically with regard to
recordkeeping), the FAA does not agree that the PMI should be tasked
with approving certain adjustments of the program. As was explained in
detail in the preamble to the supplemental NPRM, failure threshold
criteria and definitive leak/failure rate data do not exist for the
majority of the subject valves; therefore, a PMI would have no data on
which to base the approval of an extension of a leak check interval for
many valves with the assurance that the valve would not fail within the
adjusted interval. In light of this, it is essential that the FAA, at
the ACO level, have feedback as to the leak and failure rates
experienced in the field. Although the PMI's serve as the FAA's
critical link with the operators (and the PMI's oversight
responsibilities will not be minimized by this AD action), it is the
staff of the ACO that provides the engineering support necessary to
evaluate whether increases in leak check intervals will maintain an
acceptable level of safety.
Further, the FAA considers it essential that any adjustment of the
required leak check intervals, seal change intervals, and data
reporting procedures should be approved in a uniform manner in order to
ensure that the program is administered uniformly (and appropriately)
fleetwide. The staff of the Seattle ACO is in the best position to
ensure that this is accomplished. Additionally, given that possible new
relevant issues might be revealed during the approval process, it is
imperative that the engineering staff at the ACO have such feedback. In
any case, the ACO staff will work closely with the cognizant PMI to
ensure that any approved revisions to this aspect of the maintenance
program are appropriate and workable for the applicable airline.
Specific Leak Check Instructions
One commenter requests that the proposed rule be revised to include
a procedure for performing the leak checks. The commenter suggests that
the instructions contained in Boeing Service Letter 737-SL-38-3-A
(which applies to Model 737 series airplanes) be referenced in order to
ensure that all affected operators perform the same leak check. The FAA
does not concur totally. The instructions contained in Boeing Service
Letter 737-SL-38-3-A address only the forward lavatory service panel
(not the aft or executive panels), and do not correlate with the
requirement to perform a leak check of the outer cap on certain valves.
The instructions do contain procedures for performing a leak test of
the toilet tank anti-siphon (check) valve, which are appropriate for
performing that leak check in accordance with the requirements of this
AD; therefore, the FAA has added a Note to paragraphs (a)(5) and (b)(3)
to indicate that operators may consider the leak check procedures
relative to the toilet tank anti-siphon (check) valve in accordance
with the service letter as an acceptable means of compliance with those
paragraphs. The FAA does agree that a standard leak check procedure
would be beneficial, and will consider revision of this final rule to
include one if an acceptable procedure becomes available in the future.
Another commenter requests that the proposed rule be revised to
include specific procedures for conducting the leak check of the dump
valve. This commenter suggests that this leak check should be performed
by filling the toilet tank with water or rinsing fluid to a level such
that the bowl is approximately half full (at least 2 inches above the
flapper in the bowl) and waiting at least 5 minutes to determine if
leakage is present. The FAA concurs and has revised the rule to include
a new Note 1, which indicates that operators may conduct this
particular leak check in accordance with the procedures suggested by
this commenter.
Service Panel Waste Drain Cap Leak Check
Several commenters request that paragraphs (a)(1)(i) and (b)(2)(i)
of the proposed rule be revised to delete the requirement to perform a
leak check of the service panel waste drain cap that does not have an
inner door with a second positive seal. These commenters state that, to
perform this leak check, approximately 20 gallons of contaminated waste
water are required to be dumped on the ramp; such dumping violates
various environmental regulations.
The FAA does not agree that conducting this leak check will
necessarily require spilling a vast amount of waste water on the ramp.
Compliance with FAA rules is not a license to violate environmental
regulations. Operators could devise a means to catch or handle the
waste water to ensure that they will be in compliance with applicable
State or Federal environmental regulations. -
However, the FAA has reconsidered this requirement for leak checks
of the service panel waste drain cap in waste drain systems
incorporating in-line drain (ball) valves. The FAA has determined that,
for these configurations, the valve reliability is sufficient to
obviate the need for additional assurance provided by performing a leak
check of the cap, as long as a leak check of the dump valve is
accomplished. A leak check of the dump valve (in-tank valve that is
spring loaded closed and operable by a T-handle at the service panel)
can be accomplished easily and does not entail spillage of waste on the
ramp. Therefore, the FAA has revised paragraph (b)(2)(i) of the final
rule to require operators to perform a leak check of the dump valve, in
lieu of performing a leak check of the cap valve. Operators would still
be required to perform a leak check of the in-line drain (ball) valve.
The leak checks must be accompanied by visual inspections of the
service panel drain valve outer cap/door seal, the inner seal (if the
valve has an inner door/closure device with a second positive seal),
and seal mating surface for wear or damage that may cause leakage.
This revision to the requirements of the final rule does not entail
any additional burden on operators. As previously proposed, operators
would have been required to perform leak checks of both the inner and
outer doors of the cap valve and of the in-line drain valve, and a
visual inspection of the service panel drain valve outer cap/door seal.
As now required by the final rule, operators will be required to
perform fewer leak checks of valves, and one additional visual
inspection of the (inner) door seals. Since visual inspections are less
labor-intensive and less costly than leak checks, the FAA considers
that the revised requirements will significantly reduce the economic
burden on affected operators.
Similarly, the FAA has revised the requirements of paragraphs
(b)(2)(ii) and (b)(2)(iv), which require leak checks of the dump valve
and service panel valve. The final rule now specifies that the leak
check of the service panel drain valve need only entail a leak check of
the inner door/closure device (rather than leak checks of both the
inner and outer door, as was previously proposed), provided that a
visual inspection is made of the outer cap/door seal and seal mating
surface for wear or damage.
The FAA has not revised the similar requirements of paragraph
(b)(2)(iii), which pertains to drain systems incorporating ``donut''
valves. As explained later in this preamble, the reliability of this
type of valve is such that a leak test of the downstream cap is
considered necessary; therefore, paragraph (b)(2)(iii) retains the
requirement for leak checking the cap in drain system configurations
where ``donut'' valves are installed.
Waste Drain System Leak Check Procedure
One commenter requests that proposed paragraphs (a) and (b)(2) be
clarified to specify that, for drain systems that may contain more than
one kind of valve, only one of the waste drain system leak check
procedures needs to be conducted at each service panel location. The
procedure conducted should be the one that applies to the equipment
with the longest leak check interval. The FAA concurs with the
commenter's request, since this was the intent of this requirement. The
final rule has been revised to clarify this point.
Kaiser Valve Part Numbers
One commenter requests that the part number for the Kaiser
Electroprecision in-line drain valve, specified in the proposal as
``part number 2651-329-5 (or higher dash number),'' be revised to
include the entire part number 2651-329 series. The valves in this
series are all virtually identical in design and, therefore, would have
the same reliability. The FAA concurs and has revised the final rule to
call out these valves as ``Kaiser Electroprecision part number series
2651-329.''
Additionally, this same commenter requests that the proposed rule
be revised to include Kaiser Electroprecision in-line drain valves,
having part number series 2651-334 and 2651-278, in all requirements
that apply to part number series 2651-329 valves. Although these valves
differ slightly in their inlet/outlet configurations, actuating handle
sizes and shapes, and actuating handle orientation and movement, they
are identical in their main sealing components, design standards, and
principle of operation; therefore, their reliability can be assumed to
be equivalent. The FAA concurs and has revised the final rule
accordingly. Operators should note that a review of available data
indicates that the latter valve series are not currently installed on
Boeing 727 airplanes, however.
Leak Check Interval for Kaiser Valves
Other commenters request that the proposed rule be revised to
permit the Kaiser Electroprecision part number series 0218-0026 valves
(Expander Valves) to be leak checked at the same interval as the valves
listed in the supplemental NPRM for 1,000-flight hour leak checks. This
valve series was qualified to and meets the design/performance criteria
of Boeing Specification 10-62213 (Revision A). The commenter indicates
that a large number of these valves have been installed in various
transport category aircraft, and a tracking of the service history of
the installed valves reveals that over one million flight hours have
been accumulated without any reported leakage.
The FAA partially concurs with the commenter's request to provide
an extended leak check interval for this specific valve series. The FAA
considers that the presence of a forced-opening, or ``icebreaker,''
feature in a valve reduces the likelihood that service abuse will occur
that would create a leaking valve. Unlike other valves eligible for
inspections at 1,000-flight hour intervals in this rule, the Kaiser
Electroprecision part number series 0218-0026 valves do not have such
an ``icebreaker'' feature. In light of this, as well as the service
history data provided, the FAA has revised the final rule to add a new
paragraph (a)(3) to address these Kaiser Electroprecision valves and to
provide for a repetitive 600-flight hour leak check of them for those
operators electing to comply with paragraph (a) of the final rule. The
FAA has also revised paragraph (b)(2)(ii) of the final rule to include
these Kaiser Electroprecision valves in the requirements for leak
checks at 1,000 flight hour intervals. The FAA has determined that the
difference in this leak check interval between paragraph (a) and (b) is
appropriate, since the repetitive visual inspections, seal replacement
requirements, and other comprehensive aspects of paragraph (b) will
ensure that any leakage will be detected that may be caused by service
damage inflicted on the valve (due to lack of an icebreaker feature on
the valve).
Additionally, the FAA has revised the repetitive leak check
interval for the Kaiser Electroprecision valves subject to the
requirements of paragraph (b)(2)(i). That paragraph has been revised to
provide for conducting the applicable repetitive leak checks at
intervals of ``5,000 flight hours or 24 months, whichever occurs
later.'' (The supplemental NPRM proposed a repetitive leak check
interval of 5,000 flight hours only.) This provision has been made in
acknowledgment of those operators who may have related maintenance
procedures that are conducted on a schedule based on calendar time
rather than on flight hours.
Kaiser Expander Valve
One commenter has concerns about the requirements of proposed
paragraph (b)(2)(i) of the supplemental NPRM, which is applicable to
forward lavatory drain systems modified in accordance with Boeing
Service Bulletin 727-38-0021. This commenter indicates that the
proposed paragraph does not require that a Kaiser Electroprecision
Expander Valve or a lever-lock cap be installed in accordance with that
Boeing service bulletin, even though the service bulletin does refer to
such installations in certain of its modification procedures. This
commenter questions whether those installations are required to be
installed and, if so, suggests that the FAA re-issue this AD action as
a proposal to clearly indicate the intent of that paragraph.
The FAA acknowledges this commenter's concerns and agrees that
different interpretations are possible from the wording of paragraph
(b)(2)(i) as it appeared in the supplemental NPRM. The FAA has revised
the final rule to delete reference to Boeing Service Bulletin 727-38-
0021, and to merely call out the applicable Kaiser Electroprecision
part number series valves. This revision should make clear that there
is no requirement for installation of a Kaiser Electroprecision
Expander Valve to qualify for the repetitive 5,000 flight hour leak
checks. The requirement for installing a lever lock cap is contained in
paragraph (d) of the supplemental NPRM and this final rule.
Kaiser Expander Valve/In-Line Drain Valve Combination
One commenter requests that the proposed rule be revised to
establish a 6,000-flight hour leak check interval for installations of
an in-line drain valve in combination with a Kaiser Electroprecision
Expander Valve. As proposed, the leak check interval for this
combination of valves is 5,000 flight hours. The commenter provided no
justification for this request, however.
The FAA does not concur with the commenter's request. Available
data have demonstrated that the seal life and reliability of the
Expander Valve are significantly less than that of the in-line drain
valve. In light of this, an extension of the 5,000-flight hour interval
to a 6,000-flight hour interval is not justified for the in-line drain
valve in combination with the Expander Valve. However, under the
provisions of paragraph (b)(5)(i)(B) of the final rule, if an in-line
drain valve is found to have abnormal operation of the handle, the
system may continue in operation, provided a service panel drain valve
that is in the 1,000-flight hour leak check interval category is
installed in the system and has passed a leak check within the
preceding 1,000 flight hours.
Shaw Aero Valves Part Numbers
Several commenters request that the proposed rule be revised to
include Shaw Aero Devices valves in the part number 1010100B and
1010100C series in the requirements for 1,000-flight hour leak check
intervals. One of these commenters indicates that these part-numbered
valves are merely later generations of the Shaw Aero Devices part
number 1010100C-N (or higher dash number) valve, which was called out
in the supplemental NPRM and for which a 1,000-flight hour leak check
interval was proposed.
The FAA agrees that these Shaw Aero Devices valves should be
addressed in the AD, and that some increase in the leak check interval,
above the basic 200-flight hour interval, is justified for these
valves. However, the FAA does not concur with the commenters' request
to provide for a 1,000-flight hour leak check interval for them in all
circumstances. The FAA has obtained data on certain design
improvements, such as an ``ice breaker'' feature, that have been made
to certain Shaw Aero Devices valves to correct previously identified
deficiencies. Evidence indicates that Shaw Aero Devices valves having
part number 1010100B-A-1, and having serial numbers 0115 through 0121
(inclusive), 0146 through 0164 (inclusive), and 0180 and higher,
incorporate these design improvements. Therefore, the FAA has revised
paragraph (a)(2) of the final rule to include these specific valves in
the requirements for the 1,000-flight hour leak check interval.
These data also indicate that, while some Shaw Aero Devices valves
in the part number series 1010100C incorporate the ``ice breaker''
feature and have a configuration that corrects known design
deficiencies, other valves in this same series do not incorporate these
features. Therefore, not all Shaw Aero Devices part number series
1010100 are included in the 1,000-flight hour interval leak check
category. Accordingly, the FAA has revised the final rule to include a
new paragraph (a)(3), applicable to certain part number series 1010100C
valves (those without the ice breaker feature and other improvements),
which provides for a 600-flight hour leak check interval for them.
Paragraph (b)(2)(ii) of the final rule has been revised to address
these valves and provides for a 1,000-flight hour leak check interval
for them. [As explained previously, justification for the extended
interval under paragraph (b) is that the maintenance program provisions
of paragraph (b) should detect any leakage caused by service damage
inflicted due to lack of an icebreaker feature or other improvement on
the valve.] This is considered interim action, however. The FAA plans
further review of the valves in this part number series to determine if
these leak check intervals are appropriate, or whether they should be
extended or shortened.
For these same reasons, the FAA also is reviewing the valves
included in the part number 1010100C-N (and higher dash number) group,
which was called out in paragraphs (a)(2) and (b)(2)(ii) of the
supplemental NPRM. Currently, this final rule provides for a 1,000-
fight hour leak check interval for these valves. However, as more data
become available, the FAA may consider further rulemaking to address
the leak check interval for this particular valve group.
``Donut'' Valves
One commenter contends that ``donut'' valves, which are addressed
in proposed paragraph (b)(2)(iii), are unsafe and should be banned
immediately. This commenter states that these valves are of design that
has resulted in significant leakage and ``blue ice'' incidents. In
discussions with airline personnel, this commenter has found that it is
commonplace to find these valves leaking, or to find that the
``donuts'' are missing when an aircraft reaches its destination. It is
common to have the ``donut'' installed at the start of the day and find
it to be missing only one to two flights into the day. This is clearly
a dangerous situation.
The FAA acknowledges this commenter's remarks. During the past year
the FAA has received two additional reports of engine damage caused by
``blue ice'' formation from lavatory drain systems using ``donut''
valves. The FAA is continuing to review this service history of these
valves and may consider further rulemaking to require their removal
from service.
Additionally, the FAA has revised paragraph (b)(2)(iii) of the
final rule to specify certain Kaiser Roylyn part-numbered valves as
ones that incorporate the ``donut'' configuration and are, therefore,
subject to the requirements of that paragraph.
``Taco'' Valves
One commenter requests that the Kaiser Electroprecision ``taco''
valve be deleted from proposed paragraph (b)(2)(iii), which would
require that it be leak checked at intervals of 200 flight hours. The
commenter suggests that it be included in paragraph (b)(2)(iv),
instead, since that paragraph addresses similar double-door types of
valves and requires their inspection at intervals of 400 flight hours.
The FAA concurs with this request and has revised the final rule
accordingly. This change leaves only the ``donut'' valve in the
category of valves [addressed by paragraph (b)(2)(iii)] requiring leak
checks at the 200-flight hour interval. The FAA considers this
appropriate, since the ``donut'' valve clearly has been the valve
associated with the greatest number of problems relative to ``blue
ice.''
Visual Inspections To Detect Leakage
Several commenters request that paragraph (b)(4) be revised to
allow flight crew to perform the visual inspections to detect leakage.
These commenters state that, since this inspection involves only a
visual examination, trained maintenance personnel should not be made to
accomplish it.
The FAA does not concur with the commenters' request. While flight
crews are authorized to perform walk-around inspections of the
airplane, in accordance with FAR 91.7(b) [14 CFR 91.7(b)], ``Civil
aircraft airworthiness,'' there is no requirement for the flight crew
to record the results of that inspection. The FAA considers that
certified maintenance personnel are best suited to perform this
inspection due to their specific skills, training, and experience with
reporting procedures.
Flush/Fill Line Cap Installation
Several commenters request that the proposed rule be revised to
delete paragraph (d), which would require the installation of a cap on
the flush/fill lines for forward, aft, and executive lavatories. One
commenter states that the caps on the service panel are a secondary
sealing system, and that the toilet check valve is the primary seal
preventing fluid from flowing back down this line. Other commenters
also request that the requirements for periodic leak testing of the cap
be deleted. Additionally, one commenter believes that installation of a
cap on the flush/fill line will cause problems because, in their
experience, if the caps are installed, the residual flush/fill fluid
trapped inside the line will freeze by the time it reaches the next
destination; the frozen line and installed cap must be thawed out prior
to servicing of the lavatory, which can create a delay in normal
operations. This commenter and others suggest that, as an alternative
to the installation of a cap and a leak test, the proposed rule should
be revised to require periodic replacement of the seal in the toilet
tank anti-siphon (check) valve. The commenters point out that this
valve, when maintained, effectively prevents the toilet fluid from
being siphoned out through the flush/fill line, thereby making the cap
unnecessary.
The FAA does not concur with the requests to delete the requirement
for installation of a cap on the flush/fill line, but does concur that
certain alternative procedures may be provided. The FAA has received a
report of a Boeing Model 727 series airplane that experienced an in-
flight shutdown of the number 3 engine due to the ingestion of ``blue
ice'' caused by leakage from the flush/fill line. Investigation
revealed that approximately one in four of the toilet tank anti-siphon
(check) valves in the affected operator's fleet was found to leak
within a three-month period. The FAA has concluded that the anti-siphon
(check) valve alone does not appear to have sufficient integrity and
reliability to prevent leakage from the flush/fill line. However, the
FAA does acknowledge that, because the flush/fill line does not
normally have water in it and a leak test of the flush/fill line cap is
impractical in many circumstances, it is sufficient to replace the
seals in the toilet tank anti-siphon valve and the cap, and perform a
leak check of the toilet tank anti-siphon (check) valve. Paragraphs
(a)(5) and (b)(3) of the final rule have been revised to provide for
this alternative procedure.
Several commenters request that proposed paragraph (d) be revised
to delete the requirement that installation of the cap must be
accomplished only in accordance with Boeing Service Bulletin 727-38-
0021, dated July 30, 1992. That service bulletin specifies the
installation of a particular lever-lock cap; however, the commenters
request that other FAA-approved lever-lock caps also be permitted to be
used. (In their comments, certain commenters provided design and
service history data on another such lever-lock cap.) The FAA agrees
that other FAA-approved lever-lock caps are acceptable in this
installation, and has revised the final rule to specify this.
One commenter requests that any FAA approved cap, as opposed to
only lever/lock caps, be considered sufficient for the installation
required by proposed paragraph (d). The FAA does not concur, since the
commenter provided no design or service history data for any other
particular cap. However, under the provisions of paragraph (f) of the
final rule, this commenter may elect to provide such data in a request
for an alternative method of compliance with the rule.
One commenter considers that installation of a cap without a
provision for a heating element will cause ice to form in the line at
the cap. This commenter has experienced this problem on airplanes in
its fleet that are equipped with a lever-lock cap. This freezing
problem has been further exacerbated when service personnel have
damaged the caps or flush/fill line by trying to remove the ice with a
tool (such as a screw driver). The commenter suggests that the rule
should require installation of a heating element to prevent freezing in
or on the flush/fill line, and points out that Boeing Service Bulletin
727-38-0021, which is referenced in proposed paragraph (d) for the cap
installation procedures, does not call for installation of any heating
element.
The FAA agrees that one way to prevent freezing in the subject area
may be to install an FAA-approved heating element. It is also possible
to avoid the freezing problem by allowing the fluid to drain out of the
flush/fill line after servicing the tank. Since frozen flush/fill lines
are avoidable without a heating element, provided proper servicing is
done, the FAA does not consider a specific requirement to install a
heating element to be warranted.
Terminating Action
One commenter requests that installation of an in-line drain valve
per Boeing Specification S417T105 be considered terminating action for
the required leak checks. As justification for this request, the
commenter provided data indicating that, out of several million flight
hours of airplanes equipped with this particular valve, there have been
very few incidents of leakage.
The FAA does not concur with the commenter's request. Based on the
available data to date relative to all valves, the FAA has determined
that periodic leak testing of valves, as well as the replacement of
valve seals, is warranted in order to ensure that the valves do not
start to leak. Because of this, the FAA does not consider that there is
currently a ``terminating action'' for these necessary requirements.
Terminology Changes
One commenter requests that the wording of the proposed rule be
revised by changing the term ``operating torque'' to ``operation'' in
all procedures relative to inspections of the valve handle for the in-
line drain valves. This commenter points out that the actuation of
neither the in-line drain valve nor the service panel drain valve is a
rotational movement at the service panel. The FAA concurs and has
revised the terminology of the final rule accordingly.
This same commenter requests that proposed paragraph (b)(5) be
revised by changing the phrase ``blue streak findings'' to ``horizontal
blue streak findings'' when specifying which findings must be reported
to maintenance. The commenter states that this change is necessary in
order to differentiate between indications of leakage that has resulted
from spills that occurred during servicing and indications of leakage
that occurred during flight. Leakage that has occurred during flight
would be indicated by horizontal blue streaks. The FAA concurs and has
revised the terminology in the final rule accordingly.
This commenter also requests that the proposed rule be revised by
deleting the terms ``forward and aft'' when referring to ``each
lavatory * * * having an in-line drain valve installed.'' This
commenter states that some Model 727 aircraft have been built with an
executive mid-cabin lavatory with an in-line drain valve. The FAA
concurs and has revised the rule accordingly. The intent of the rule is
clear that the related procedures are to be performed on ``each''
lavatory having the subject drain valve, regardless of where the
lavatory is located on the airplane.
This commenter further points out that the terms ``service panel
drain valve,'' ``cap valve,'' and ``drain valve at the service panel''
are used in various places throughout the proposed rule to describe the
same valve. The commenter suggests that, in order to be consistent, the
rule be revised to call this valve ``the service panel drain valve'' in
all pertinent references. The FAA concurs and has revised the final
rule accordingly. For similar reasons, the final rule has been revised
by changing the term ``ball valve'' to ``in-line drain valve'' in
several places.
Estimated Cost Figures
Several operators state that the estimated cost impact of the rule,
as presented in the preamble to the supplemental NPRM, is too low and
should be revised to reflect estimates of the costs as submitted by
these individual operators. The FAA does not concur that the estimated
cost impact figure need to be revised. While it is reasonable to assume
that the costs to some operators may be higher than those presented in
this preamble, it is also reasonable to assume that the costs to other
operators may be considerably lower. Therefore, the estimated cost
impact represents an average for the U.S. fleet, based on the best data
available to date. The FAA considers the cost impact estimate, as
presented, to be sufficiently accurate for the purposes of this
rulemaking action.
Cost Impact
There are approximately 1,752 Boeing Model 727 series airplanes of
the affected design in the worldwide fleet, operated by 153 operators.
It is estimated that 1,277 airplanes of U.S. registry and 54 U.S.
operators will be affected by this AD.
The FAA estimates that it will take approximately 4 work hours per
airplane lavatory drain (normally, there are 2 drains per airplane) to
accomplish a leak check, at an average labor cost of $55 per work hour.
Certain airplanes (i.e., those that have ``donut'' type of drain
valve installed) may be required to be leak checked as many as 15 times
each year. Certain other airplanes having other valve configurations
will be required to be leak checked as few as 3 times each year. Some
airplanes that have various combinations drain valves installed will
require approximately 2 leak checks of one drain valve and 3 leak
checks of the other drain valve each year. Based on these figures, the
total annual (recurring) cost impact of the required repetitive leak
checks on U.S. operators is estimated to be between $6,600 and $1,320
per airplane per year.
The FAA estimates that it will take approximately 1 work hour per
airplane lavatory drain to accomplish a visual inspection of the
service panel drain valve cap/door seal and seal mating surfaces, at an
average labor cost of $55 per work hour.
As with leak checks, certain airplanes will be required to be
visually inspected as many as 15 times or as few as 3 times each year.
Based on these figures, the total annual (recurring) cost impact of the
required repetitive visual inspections on U.S. operators is estimated
to be between $825 and $165 per airplane per year.
The 1,277 affected airplanes of U.S. registry have, on an average,
3 flush/fill lines per airplane. The FAA estimates that the
installation of a level lock cap assembly will require approximately 2
work hours to accomplish, at an average labor cost of $55 per work
hour. Required parts are estimated to be $275 per drain installation.
Based on these figures, the total cost impact of the requirement to
install a cap on the flush/fill lines is estimated to be $1,474,935, or
an average of $1,155 per airplane.
The number of required work hours, as indicated above, is presented
as if the accomplishment of the actions proposed in this AD were to be
conducted as ``stand alone'' actions. However, in actual practice,
these actions could be accomplished coincidentally or in combination
with normally scheduled airplane inspections and other maintenance
program tasks. Therefore, the actual number of necessary ``additional''
work hours will be minimal in many instances. Additionally, any costs
associated with special airplane scheduling should be minimal.
In addition to the costs discussed above, for those operators who
elect to comply with proposed paragraph (b) of this AD action, the FAA
estimates that it will take approximately 40 work hours per operator to
incorporate the lavatory drain system leak check procedures into the
maintenance programs, at an average labor cost of $55 per work hour.
Based on these figures, the total cost impact of the proposed
maintenance revision requirement of this AD action on the 54 U.S.
operators is estimated to be $118,800, or $2,200 per operator.
The ``total cost impact'' figures described above are based on
assumptions that no operator has yet accomplished any of the
requirements of this AD action, and no operator would accomplish those
actions in the future if this AD were not adopted.
The FAA recognizes that the obligation to maintain aircraft in an
airworthy condition is vital, but sometimes expensive. Because AD's
require specific actions to address specific unsafe conditions, they
appear to impose costs that would not otherwise be borne by operators.
However, because of the general obligation of operators to maintain
aircraft in an airworthy condition, this appearance is deceptive.
Attributing those costs solely to the issuance of this AD is
unrealistic because, in the interest of maintaining safe aircraft,
prudent operators would accomplish the required actions even if they
were not required to do so by the AD.
A full cost-benefit analysis has not been accomplished for this AD.
As a matter of law, in order to be airworthy, an aircraft must conform
to its type design and be in a condition for safe operation. The type
design is approved only after the FAA makes a determination that it
complies with all applicable airworthiness requirements. In adopting
and maintaining those requirements, the FAA has already made the
determination that they establish a level of safety that is cost-
beneficial. When the FAA, as in this AD, makes a finding of an unsafe
condition, this means that the original cost-beneficial level of safety
is no longer being achieved and that the required actions are necessary
to restore that level of safety. Because this level of safety has
already been determined to be cost-beneficial, a full cost-benefit
analysis for this AD would be redundant and unnecessary.
Regulatory Impact
The regulations adopted herein will not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this final
rule does not have sufficient federalism implications to warrant the
preparation of a Federalism Assessment.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
Flexibility Act. A final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it may be obtained
from the Rules Docket at the location provided under the caption
ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-5250 (51 FR
7767, March 6, 1986), and by adding a new airworthiness directive (AD),
amendment 39-9073, to read as follows:
94-23-10 Boeing: Amendment 39-9073, Docket No. 90-NM-265-AD.
Supersedes AD 86-05-07, Amendment 39-5250.
Applicability: All Model 727 series airplanes, certificated in
any category.
Compliance: Required as indicated, unless previously
accomplished.
To prevent engine damage or separation, airframe damage, and/or
hazard to persons or property on the ground as a result of ``blue
ice'' that has formed from leakage of the lavatory drain system and
dislodged from the airplane, accomplish the following:
Note 1: The dump valve leak checks required by this AD may be
performed by filling the toilet tank with water/rinsing fluid to a
level such that the bowl is approximately half full (at least 2
inches above the flapper in the bowl) and checking for leakage after
a period of 5 minutes.
(a) Except as provided in paragraph (b) of this AD, accomplish
the applicable procedures specified in paragraphs (a)(1), (a)(2),
(a)(3), (a)(4), (a)(5) and (a)(6) of this AD. If the waste drain
system incorporates more than one type of valve, only one of the
waste drain system leak check procedures (the one that applies to
the equipment with the longest leak check interval) must be
conducted at each service panel location.
(1) For each lavatory drain system that has an in-line drain
valve installed, Kaiser Electroprecision part number series 2651-
329, 2651-334, or 2651-278: Within 1,500 flight hours after the
effective date of this AD, and thereafter at intervals not to exceed
1,500 flight hours, accomplish the following:
(i) Conduct a leak check of the dump valve (in-tank valve that
is spring loaded closed and operable by a T-handle at the service
panel) and the in-line drain valve. The in-line drain valve leak
check must be performed with a minimum of 3 pounds per square inch
differential pressure (PSID) applied across the valve. -
(ii) Visually inspect the service panel drain valve outer cap
seal and the inner seal (if the valve has an inner door/closure
device with a second positive seal), and the seal mating surfaces,
for wear or damage that may allow leakage. Prior to further flight,
replace any worn or damaged seal, and repair or replace any damaged
seal mating surfaces, in accordance with the valve manufacturer's
maintenance manual.
(2) For each lavatory drain system that has a service panel
drain valve installed, Kaiser Electroprecision part number series
0218-0032; or Shaw Aero Devices part number 1010100C-N (or higher
dash number); or Shaw Aero Devices part number 1010100B-A-1, serial
numbers 0115 through 0121, 0146 through 0164, and -0180 and higher;
or Pneudraulics part number series 9527: Within 1,000 flight hours
after the effective date of this AD, and thereafter at intervals not
to exceed 1,000 flight hours, conduct a leak check of the dump valve
and drain valve. The service panel drain valve leak check must be
performed with a minimum of 3 PSID applied across the valve. Both
the inner door/closure device and the outer cap/door must be leak
checked.
(3) For each lavatory drain system that has a service panel
drain valve installed, Kaiser Electroprecision part number series
0218-0026, or Shaw Aero Devices part number series 1010100C (except
as called out in paragraph (a)(2) above), or Shaw Aero Devices part
number 1010100B (except as called out in paragraph (a)(2) above):
Within 600 flight hours after the effective date of this AD, and
thereafter at intervals not to exceed 600 flight hours, conduct a
leak check of the dump valve and the service panel drain valve. The
service panel drain valve leak check must be performed with a
minimum 3 PSID applied across the valve. Both the inner door/closure
device and the outer cap/door must be leak checked.
(4) For each lavatory drain system not addressed in paragraph
(a)(1), (a)(2), or (a)(3) of this AD: Within 200 flight hours after
the effective date of this AD, and thereafter at intervals not to
exceed 200 flight hours, conduct a leak check of the dump valve and
the service panel drain valve. The service panel drain valve leak
check must be performed with a minimum 3 PSID applied across the
valve. If the service panel drain valve has an inner door with a
second positive seal, both the inner door and the outer cap/door
must be leak checked.
(5) For flush/fill lines: Within 5,000 flight hours after the
effective date of this AD, and thereafter at intervals not to exceed
5,000 flight hours, accomplish either of the following procedures
specified in paragraphs (a)(5)(i) or (a)(5)(ii) of this AD:
(i) Conduct a leak check of the flush/fill line cap. This leak
check must be made with a minimum of 3 PSID applied across the cap.
Or
(ii) Replace the seals on the toilet tank anti-siphon (check)
valve and the flush/fill line cap. Additionally, perform a leak
check of the toilet tank anti-siphon (check) valve with a minimum of
3 PSID across the valve.
-Note 2: The leak test procedure specified in Boeing Service
Letter 737-SL-38-3-A, dated March 19, 1990, may be referred to as
guidance for the procedures required by this paragraph.
(6) If a leak is discovered during any leak check required by
paragraph (a) of this AD, prior to further flight, accomplish one of
the following procedures:
(i) Repair the leak; or
(ii) Drain the affected lavatory system and placard the lavatory
inoperative until repairs can be accomplished.
(b) As an alternative to the requirements of paragraph (a) of
this AD: Within 180 days after the effective date of this AD, revise
the FAA-approved maintenance program to include the requirements
specified in paragraphs (b)(1), (b)(2), (b)(3), (b)(4), (b)(5), and
(b)(6) of this AD.
(1) Replace the valve seals in accordance with the applicable
schedule specified in paragraphs (b)(1)(i) and (b)(1)(ii) of this
AD. Any revision to this replacement schedule must be approved by
the Manager, Seattle Aircraft Certification Office (ACO), FAA,
Transport Airplane Directorate.
(i) For each lavatory drain system that has an in-line drain
valve installed, Kaiser Electroprecision part number series 2651-
329, 2651-334, or 2651-278: Replace the seals within 5,000 flight
hours after revision of the maintenance program in accordance with
paragraph (b) of this AD, and thereafter at intervals not to exceed
52 months.
(ii) For each lavatory drain system that has any other type of
drain valve: Replace the seals within 5,000 flight hours after
revision of the maintenance program in accordance with paragraph (b)
of this AD, and thereafter at intervals not to exceed 18 months.
(2) Conduct periodic leak checks of the lavatory drain systems
in accordance with the applicable schedule specified in paragraphs
(b)(2)(i), (b)(2)(ii), (b)(2)(iii), and (b)(2)(iv) of this AD. If
the waste drain system incorporates more than one type of valve,
only one of the waste drain system leak check procedures (the one
that applies to the equipment with the longest leak check interval)
must be conducted at each service panel location. Any revision to
the leak check schedule must be approved by the Manager, Seattle
ACO, FAA, Transport Airplane Directorate.
(i) For each lavatory drain system that has an in-line drain
valve, Kaiser Electroprecision part number series 2651-278, 2651-
329, or 2651-334: Within 5,000 flight hours after revision of the
maintenance program in accordance with paragraph (b) of this AD, and
thereafter at intervals not to exceed 24 months or 5,000 flight
hours, whichever occurs later, accomplish the procedures specified
in paragraphs (b)(2)(i)(A) and (b)(2)(i)(B) of this AD: -
(A) Conduct a leak check of the dump valve (in-tank valve that
is spring loaded, closed and operable by a T-handle at the service
panel), and in-line drain valve. The in-line drain valve leak check
must be performed with a minimum of 3 pounds per square inch
differential pressure (PSID) applied across the valve.
(B) Visually inspect the service panel drain valve outer cap/
door seal and the inner seal (if the valve has an inner door/closure
device with a second positive seal) and seal mating surface for wear
or damage that may cause leakage. Any worn or damaged seal must be
replaced and any damaged seal mating surface must be repaired or
replaced, prior to further flight, in accordance with the valve
manufacturer's maintenance manual.
(ii) For each lavatory drain system that has a service panel
drain valve installed, Kaiser Electroprecision part number series
0218-0032, or Kaiser Electroprecision part number series 0218-0026,
or Shaw Aero Devices part number series 1010100C, or Shaw Aero
Devises part number series 1010100B, or Pneudraulics part number
series 9527: Within 1,000 flight hours after revising the
maintenance program in accordance with paragraph (b) of this AD, and
thereafter at intervals not to exceed 1,000 flight hours, accomplish
the procedures specified in paragraphs (b)(2)(ii)(A) and
(b)(2)(ii)(B) of this AD:
(A) Conduct leak checks of the dump valve and service panel
drain valve. The service panel drain valve leak check must be
performed with a minimum of 3 PSID applied across the valve. Only
the inner door/closure device of the service panel drain valve must
be leak checked.
(B) Visually inspect the service panel drain valve outer cap/
door seal and seal mating surface for wear or damage that may cause
leakage. Any worn or damaged seal must be replaced, and any damaged
seal mating surface must be repaired or replaced, prior to further
flight, in accordance with the valve manufacturer's maintenance
manual.
(iii) For each lavatory drain system with a lavatory drain
system valve that either incorporates ``donut'' assemblies (or
substitute assemblies from another manufacturer) Kaiser
Electroprecision part number 4259-20 or 4259-31, or incorporates
Kaiser Roylyn part number 2651-194C, 2651-197C, 2651-216, 2651-219,
2651-235, 2651-256, 2651-258, 2651-259, 2651-260, 2651-275, 2651-
282, or 2651-286: Within 200 flight hours after revising the
maintenance program in accordance with paragraph (b) of this AD, and
thereafter at intervals not to exceed 200 flight hours, conduct leak
checks of the dump valve and the service panel drain valve. The
service panel drain valve leak check must be performed with a
minimum 3 PSID applied across the valve. Both the donut and the
outer cap/door must be leak checked.
(iv) For each lavatory drain system that incorporates any other
type of approved valves: Within 400 flight hours after revising the
maintenance program in accordance with paragraph (b) of this AD, and
thereafter at intervals not to exceed 400 flight hours accomplish
the procedures specified in paragraphs (b)(2)(iv)(A) and
(b)(2)(iv)(B) of this AD:
(A) Conduct leak checks of the dump valve and the service panel
drain valve. The service panel drain valve leak check must be
performed with a minimum 3 PSID applied across the valve. If the
service panel drain valve has an inner door/closure device with a
second positive seal, only the inner door must be leak checked.
(B) If the valve has an inner door/closure device with a second
positive seal: Visually inspect the service panel drain valve outer
door/cap seal and seal mating surface for wear or damage that may
cause leakage. Any worn or damaged seal must be replaced and any
damaged seal mating surface must be repaired or replaced, prior to
further flight, in accordance with the valve manufacturer's
maintenance manual.
(3) For flush/fill lines: Within 5,000 flight hours after the
effective date of this AD, and thereafter at intervals not to exceed
5,000 flight hours, accomplish either of the procedures specified in
paragraphs (b)(3)(i) or (b)(3)(ii) of this AD:
(i) Conduct a leak check of the flush/fill line cap. This leak
check must be made with a minimum of 3 PSID applied across the cap.
Or
(ii) Replace the seals on the toilet tank anti-siphon (check)
valve and the flush/fill line cap. Additionally, perform a leak
check of the toilet tank anti-siphon (check) valve with a minimum of
3 PSID across the valve.
Note 3: The leak test procedure specified in Boeing Service
Letter 737-SL-38-3-A, dated March 19, 1990, may be referred to as
guidance for the procedures required by this paragraph.
(4) Provide procedures for accomplishing visual inspections to
detect leakage, to be conducted by maintenance personnel at
intervals not to exceed 4 calendar days or 45 flight hours,
whichever occurs later.
(5) Provide procedures for reporting leakage. These procedures
shall provide that any ``horizontal blue streak'' findings must be
reported to maintenance and that, prior to further flight, the
leaking system shall either be repaired, or be drained and placarded
inoperative.
(i) For systems incorporating an in-line drain valve, Kaiser
Electroprecision part number series 2651-278, 2651-329, or 2651-334:
The reporting procedures must include provisions for reporting to
maintenance any instances of abnormal operation of the valve handle
for the in-line drain valve, as observed by service personnel during
normal servicing.
(A) Additionally, these provisions must include procedures for
either: prior to further flight, following the in-line drain valve
manufacturer's recommended troubleshooting procedures and correction
of the discrepancy; or prior to further flight, draining the
lavatory system and placarding it inoperative until the correction
of the discrepancy can be accomplished.
(B) If the drain system also includes an additional service
panel drain valve, Kaiser Electroprecision part number series 0218-
0026 or 0218-0032, or Shaw Aero Devices part number series 1010100C
or 1010100B, or Pneudraulics part number series 9527, indications of
abnormal operation of the valve handle for the in-line drain valve
need not be addressed immediately if a leak check of the service
panel drain valve indicates no leakage or other discrepancy. In
these cases, repair of the in-line drain valve must be accomplished
within 1,000 flight hours after the leak check of the additional
service panel drain valve.
(6) Provide training programs for maintenance and servicing
personnel that include information on ``Blue Ice Awareness'' and the
hazards of ``blue ice.''
(c) For operators who elect to comply with paragraph (b) of this
AD: Any revision to (i.e., extension of) the leak check intervals
required by paragraph (b) of this AD must be approved by the
Manager, Seattle ACO, FAA, Transport Airplane Directorate. Requests
for such revisions must be submitted to the Manager of the Seattle
ACO through the FAA Principal Maintenance Inspector (PMI), and must
include the following information:
(1) The operator's name;
(2) A statement verifying that all known cases/indications of
leakage or failed leak tests are included in the submitted material;
(3) The type of valve (make, model, manufacturer, vendor part
number, and serial number);
(4) The period of time covered by the data;
(5) The current FAA leak check interval;
(6) Whether or not seals have been replaced between the seal
replacement intervals required by this AD; -
(7) Whether or not leakage has been detected between leak check
intervals required by this AD, and the reason for leakage (i.e.,
worn seals, foreign materials on sealing surface, scratched or
damaged sealing surface or valve, etc.); -
(8) Whether or not any leak check was conducted without first
inspecting or cleaning the sealing surfaces, changing the seals, or
repairing the valve. [If such activities have been accomplished
prior to conducting the periodic leak check, that leak check shall
be recorded as a ``failure'' for purposes of the data required for
this request submission. The exception to this is the normally
scheduled seal change in accordance with paragraph (b)(1) of this
AD. Performing this scheduled seal change prior to a leak check will
not cause that leak check to be recorded as a failure.]
-Note 4: Requests for approval of revised leak check intervals
may be submitted in any format, provided that the data give the same
level of assurance specified in paragraph (c) of this AD.
-Note 5: For the purposes of expediting resolution of requests
for revisions to the leak check intervals, the FAA suggests that the
requester summarize the raw data; group the data gathered from
different airplanes (of the same model) and drain systems with the
same kind of valve; and provide a recommendation from pertinent
industry group(s) and/or the manufacturer specifying an appropriate
revised leak check interval.
-(d) For all airplanes: Within 5,000 flight hours after the
effective date of this AD, install a lever/lock cap on the flush/
fill lines for forward, aft, and executive lavatories. The cap must
be either an FAA-approved lever/lock cap, or a cap installed in
accordance with Boeing Service Bulletin 727-38-0021, dated July 30,
1992. -
(e) For any affected airplane acquired after the effective date
of this AD: Before any operator places into service any airplane
subject to the requirements of this AD, a schedule for the
accomplishment of the leak checks required by this AD shall be
established in accordance with either paragraph (e)(1) or (e)(2) of
this AD, as applicable. After each leak check has been performed
once, each subsequent leak check must be performed in accordance
with the new operator's schedule, in accordance with either
paragraph (a) or (b) of this AD as applicable. -
(1) For airplanes previously maintained in accordance with this
AD, the first leak check to be performed by the new operator must be
accomplished in accordance with the previous operator's schedule or
with the new operator's schedule, whichever would result in the
earlier accomplishment date for that leak check. -
(2) For airplanes that have not been previously maintained in
accordance with this AD, the first leak check to be performed by the
new operator must be accomplished prior to further flight, or in
accordance with a schedule approved by the FAA PMI, but within a
period not to exceed 200 flight hours. -
(f) An alternative method of compliance or adjustment of the
compliance time that provides an acceptable level of safety may be
used if approved by the Manager, Seattle ACO, FAA, Transport
Airplane Directorate. Operators shall submit their requests through
an appropriate FAA PMI, who may add comments and then send it to the
Manager, Seattle ACO.
-Note 6: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
-Note 7: For any valve that is not eligible for the extended
leak check intervals of this AD: To be eligible for the leak check
interval specified in paragraphs (a)(1), (a)(2), (b)(2)(i), and
(b)(2)(ii), the service history data of the valve must be submitted
to the Manager, Seattle ACO, FAA, Transport Airplane Directorate,
with a request for an alternative method of compliance with this AD.
The request should include an analysis of known failure modes for
the valve, if it is an existing design, and known failure modes of
similar valves. Additionally, the request should include an
explanation of how design features will preclude these failure
modes, results of qualification tests, and approximately 25,000
flight hours or 25,000 flight cycles of service history data,
including a winter season, collected in accordance with the
requirements of paragraph (c) of this AD or a similar program. One
of the factors that the FAA will consider in approving alternative
valve designs is whether the valve meets Boeing Specification
S417T105 or 10-62213; however, meeting the Boeing specification is
not a prerequisite for approval of alternative valve designs.
-(g) Special flight permits may be issued in accordance with
sections 21.197 and 21.199 of the Federal Aviation Regulations (14
CFR 21.197 and 21.199) to operate the airplane to a location where
the requirements of this AD can be accomplished. -
(h) This amendment becomes effective on December 16, 1994.
Issued in Renton, Washington, on November 9, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-28243 Filed 11-15-94; 8:45 am]
BILLING CODE 4910-13-U